Method of treating oil wells



June5, 1945. E. A. sTEPHENsoN 2,377,529

\ METHOD 0F TREATING OIL WELLS Filed Nov. 8, 1943 BY s ATTORNEY.

Patented June 5, 1945 UNITED s'mrizysN PATENT- ori-lcs l ME'IHTOD OF lTREATIIING OIL WELLS Eugene A. Stephenson, Lawrence, Kans., assgnor tw The University of Kansas Research Foundation, Lawrence, Kans., a corporation of Kanhpplication November 8, 194,3, Serial No. 509,372

(el. 16e- 21) i i Y of apparatus about to be described, the same will be' capable of a large numberof specific applica- 2 Claims.

bearing formations,` which includes the steps-of forcing oil into the water bearing portion of said formation at a velocity and pressure sufficient 'to increase the oil saturation within the said formation and to inhibit the entrance of water into the well.

A further object of the invention is the provision of a method of treating 'oil wells which includes the steps of forcing oil into the water bearing portion of the producing formation at a velocity and pressure sufficient to increase the oil saturation within the formation around the well bore to inhibit the entrance of water4 into the well because of the formation of an emulsion.

This application is a continuation in part of my co-pending application Serial No. 492,700, led June 29, 1943, for Method and apparatus for treating oil wells.

tions. For example, in the treatment of wells used in artificial water flooding operations where it becomes desirable to reduce the permeability. of

streaks of the formation into ywhich excessive portions of injected Vwater penetrate and thus reduce the effectiveness of the flooding process in other less permeable streaks.

The method is also applicabletot e treatment of high gas-oil ratio wellsthroug'h vthe injection of oil under pressure into selected portions of the producing formation.

'I'he drawing illustrates an oil well partially in section, having apparatus associated therewith that permits practicing the method embodying this invention.

A still further object of the invention is the' provision of a method of treating oil Wells wherein a column of oil and water has appeared, which includes segregating a portion of the well bore to set off a part of the face of the producing formation, and thereafter introducing oil under high pressure into the segregatedportion and thence into the said formation to displace the water therein.

This invention has'for a further object to provide novel, simple, and efficient apparatus for carrying out the several steps of the aforementioned method.

Another object ofthe invention is to `provide apparatus for segregating a portion of the well bore, whereby one of the stepsof the invention may be pra-cticed, i. e., that of injecting oil under high pressure into a selected part of the forma-l tion.

A further object of the -invention is to,provide an apparatus for treating oil-water wlls that permits segregating `a portion of fthe well bore forthe-injectionof .oil under high pressure vinto a selected part of the formation without rst removing the water from the well.

When practicing the invention `as set forth in theforegoing objects, and through employment In the drawing, numeral 2 designates the conventional casing which hasits end 4 spaced from the bottom of the bore 6. In some practices 2' extends to the bottomof the well and is perforated adjacent to thel producing section of the formation. Cement 56 fills 4the space vbetween casing 2 and the natural rock 58. Upon the free end of casing 2'is a conventional high pressure casing lhead il with suitable packing therein through which tubing I4 extends to a cross l0.

One opening' of the cross4 l0 is connectedby means of pipe l2, withvalve i6 therein, to gauge i8 for the measurement of the pressure in tubin g i4. One side of the cross l0 is connected-by pipe I4, or v for the connection of other devices which are commonly used for the measurement of fluid levels in oil wells. A valve 44 should be interposed in pipe 42.

Similarly pipe 5I) having valve 52 placed therein, is attached to the other opening 4irrcasing head 8 through which iiuid 'may be introducedfromtank or pump (not shown), into the space 48 betweenrtubing I4 and casing 2.

The oil producing formation is of a character.

that might be encountered at any location where artificial water drive, or drive due to solution I gas r gaS Cap gais. L

the degree of abruptness at 30, but is usually characterized by low water saturation in the lower part of 24' and the upper part of 26 with progressive increase in water saturation with depth below the oil-water contact 30. The contact zone is normally the zone in which capillary rise exists above a xed plane of complete water saturation. Similarly, the gas-oil contact (not shown), represents a. zone of progressively greater oil saturation when passing from gasto oil zones. The rate of increase in water saturation with depth in zone 2li-M26, is also a function of the permeabilities of the various streaks within the formation. Zone 24'-26 .may also contain'slugs or pockets of oil which may become recoverable through the reduction in permeability to water in zone 2 4-26.

Area 28 is a diagrammatioal representation of what is commonly designated as a water-cone L* in and-around oil-water producing wells. Within such area 28 the natural` oil-water saturations have been greatlymodified by water encroach-` The line of demarkation between 24 and 26 varies 'in 33 permits passage of oil into chamber 40 and thence through the walls of bore 6 into the ment and the formation thus represented has become more permeable toI water than to oil.

f Such cracks or streaks are not illustrated but are well known to those skilled in the art.

The liquid'column 32 in well bore 6 usually I comprises both oil and water when the necessity for treating the well, in accordance with this method, arises.

In practice of the invention, one of the ilrst steps is to prepare the well for treatment by shut- 'ting it down, or in other terminology, allow the well to stand idle, for a short time so as to reach an approximately stable condition. The exact time will depend upon ,many factors, but the principal ones will be the productivity of holeas additional joints of pipe are added to tubing i4. When the proper length of tubing has been placed in the hole, packing 34 is expanded to set oil? the lower portion of boref from that part thereof above seal 34, to 'form chamber 40. When oil or other selected -Yliquid is pumped into the bottom of bore 6 through tubing I4,

section 36 and back pressure valvel 38, disposition of packing 34 insures separation of that section of the well bore opposite the predominantly.

water-producing formation 26-28 from that section of the well bore opposite the predominantly oil bearing portion of the formation 2,4. Valve water bearing portion of the formation, but prevents any reverse qmovement of liquid into tubing section 36-i4 from bore 6.

The effectiveness of the seal between 34 and the .surrounding formation may be greatly iniproved by the addition of oil on top of oil-water i column 32 in annular space 48 through pipe 50 and the casing head 8.'until said annular space is full.

When pumping oil into that part of bore 6 below packing 34 (chamber 40), the pressure of injection should be as great as is practicable to cause 'the oil to enter the formation 26 and 28 at the highest possible rate, s'o as to reduce the permeability to oil of thewater bearing portion of the formation and stimulate the formation of an emulsion within the water ybearing portion ofthe formation. With a portion of bore 6 segregated by seal 3, it is possibleto inject oil ata rate sui'liciently high to form an emulsion of oil and water within the spaces of the formation 2li- 26, vwhereby to inhibit entrance of water into bore 6.

Crude oil which hasbeen' produced from the formation to be treated should preferably be used f since such oil will be more or less in equilibrium the well itself, the permeability of the formation, "the formation pressure, the depth of the well, the production histor and the physical properties of the oil. In actual practice it has been found that many Wells reach an equilibrium condition within a period of a few hours, While others require a 'few days, and others many days. However, those which require extended periods in order to become stabilized, are for all practical purposes, stable during the short period of/time which would be-required for their treat- `ment according' to the method of this invention;

It has been discovered in practice of this in` vention, that if the oil-water wells are permitted to .remain idle fory a`\ few days-10 to 20-that Y inlmany cases all of the water in said wells will i valve 38 at its lower end. Packing 34 is also carried by section- 36, which is lowered into the 'sui-table liquids may be used.

specially designed to increase stability (potency),V of any emulsion, are available on the openv market.

Having thus described the invention, what is claimed as new and desired to be securedby Letters Patent is:

1. The method of treating an oil well which vpenetrates an oil-and water bearing formation and that has a liquid column consisting of both oil and water, which includes the step of setting oi a portion of the well bore to create a closed chamber partially walled by the o il and water vbearing formation, and injecting oil into said closed chamber' at a lrate suiiicien'tly great l penetrates an oil-and water bearing formation to form an emulsion of oil and water within the interstices of the formation.

2. The method of treating an oil well which and that has a liquid column consisting of both oiland water, which includes the -step of setting oif a portion of lthe wellbore to create a closedl chamber partially walled by the oil and water bearing formation, and injecting oilinto said closed chamber at a velocity in excess of that at which the well has previously been produced and at a rate sufficiently great -to form an emulsion of oil and water within the interstices of the 

